With the rapid increase in communications traffic, authorized spectrums of the 3rd Generation Partner Project (3GPP) are increasingly insufficient to provide higher network capacity, such as an LTE network. In order to further improve the utilization of spectrum resources, 3GPP is discussing how to use unauthorized spectrums such as 2.4 GHz and 5 GHz band with the help of authorized spectrums. The unauthorized spectrum is currently mainly used for Wi-Fi, Bluetooth, radar, medical systems, and the like.
However, in the LTE network, the interference level is ensured by good orthogonality, and uplink/downlink transmission between a base station and a user does not have to consider whether there are other base stations or other users in the transmission of data. If the LTE operates in the unlicensed frequency band without considering whether there are other devices using the unlicensed frequency band, it will bring great interference to Wi-Fi devices. In LTE system, transmission will be performed as long as there is a service and there is no monitoring rules, therefore, a Wi-Fi device cannot perform transmission if the LTE system has service to transmit, and data can only be transmitted by the Wi-Fi device when it is detected that channel is idle after the service transmission of the LTE system is finished.
Therefore, how to prevent a LTE system operating in an unlicensed frequency band from causing great interference to other systems while ensuring normal operation of the LTE system in the unlicensed frequency band has become a technical problem to be solved urgently.